Hi Paul,
We had a similar issue and had a pool specialist repair it.
His name is Roman and his telephone number is
+34 673 720 116.
In our case, the skimmer cracked and was leaking water continuously.
After initial digging to replace the skimmers, he showed us where a lot of the drainage pipe around the pool underground was made from flexible weaker piping as opposed to rigid pipework and was showing signs of cracking.
We bit the bullet and had it all replaced with rigid pipework (that ideally should have been used first day).
A water leak here would have proved more costly as water is expensive....the price goes up dramatically the more you use, which is exactly what happens in the case of a leak)
Best regards,
Brandon